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Roberts Sensitive Sangeans

A couple of Roberts branded Sangean sets that are both faulty, but still manage to bring in the DX. I already have the R816 (ATS-909) so my curiosity got the better of me to see how the lesser models from that era perform.

Roberts R617 is the Sangean ATS-606, early version with a DISPLAY button. The later models have a FINE tune in this position instead which allows 1kHz tuning steps. This one runs OK for a while and then the PLL circuit will lock up. At present, proving elusive to find the cause.


Roberts R809 is the Sangean ATS-808. This one came to me faulty as it's obviously suffered display damage. Also had a 1kHz tone present on all the LW/MW/SW signals. Applying an unmodulated test signal, the tone got louder as I increased the RF level! After testing some suspicious capacitors around the PLL circuitry and finding them to be OK, I found contamination in various places on the microprocessor/keypad board which I've cleaned up and it now works. Another parts donor is on the way.


Given the difference in sizes, the electronic design seems to be very similar. Both of these sets have poor front-end selectivity on MW - I found a signal on 576kHz which, after the initial "a new station!" excitement, turned out to be an image product of CWR on 1476kHz! (twice the second IF 450kHz). Happy to say that I don't notice that on the R861. They also accept an external antenna for LW and MW.


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